"I used to drink 18 litres of coke a day about 18 years ago," said the 38-year-old mother of four. "I stopped drinking about 15 years ago. I just built up to it, just got used to it. It's a mad thing to do, a mad thing to do."

Mrs Wyatt said she was the victim of an attack when she was 16, and believed that this event led to, and fed, her Coke addiction.

"It's all mental. If something happens in your life, a lot of people turn to drugs or alcohol, and for a lot of bigger people they turn to food. We're all like it."

Mrs Wyatt still struggles to believe how addicted she became.

"We had bottles for Africa – and I didn't even know I was drinking that much. I even had a bottle of Coke beside my bed so when I'd wake up in the middle of the night I'd have a glass of Coke."

I can't believe I drank that much, that I could even fit it in there," she said.

Apart from weight gain and the odd bout of irritability she experienced from not having her daily dose, the effect of the excessive consumption went largely unnoticed at the time.

Mrs Wyatt's weight shot up more than 100kg during those three dark years, from 92kg to 198kg at her heaviest, and all the while she continued the habit.

However she got a wake up call one day while drinking a glass of Coke. She felt pain shooting up her arm and through the back of her shoulder. On her mother's advice, she drove up to Wairau Hospital for a check-up.

"I thought I was having a heart attack, but it wasn't – it was just a scare." They advised me not to have any more caffeine.

"I made the decision myself," she said.

"I didn't do it slowly. I had boxes of it sitting there in the house, and I tipped all 30 bottles of it down the sink.